The present invention relates generally to fluid ejection devices, and more particularly to a substrate for a fluid ejection device.
In some fluid ejection devices, such as printheads, a drop ejecting element is formed on a front side of a substrate and fluid is routed to an ejection chamber of the drop ejecting element through an opening or slot in the substrate. Often, the substrate is a silicon wafer and the slot is formed in the wafer by chemical etching. Existing methods of forming the slot through the substrate include etching into the substrate from the backside of the substrate to the front side of the substrate. The backside of the substrate is defined as a side of the substrate opposite of which the drop ejecting element is formed. Unfortunately, etching into the substrate from the backside all the way to the front side may result in misalignment of the slot at the front side and/or varying width of the slot at the front side.
Accordingly, it is desired to control formation of the slot through the substrate.
A method of forming an opening through a substrate having a first side and a second side opposite the first side includes forming a trench in the first side of the substrate, forming a mask layer within the trench, forming at least one hole in the mask layer, filling the trench and the at least one hole, forming a first portion of the opening in the substrate from the second side of the substrate to the mask layer, and forming a second portion of the opening in the substrate from the second side of the substrate through the at least one hole in the mask layer to the first side of the substrate.